Stopping without standing still
Chronograph and rattrapante mechanism

There are always special moments in life that make people wish they could freeze time and prolong experiences of joy and elation for just a while longer. Although it is not possible to stop time and preserve such moments for eternity, Lange chronographs can measure the duration of such events and others very accurately.

Our chronographs and their movements that were developed in-house have been icons of the manufactory since 1999. The elaborate constructions are based on the column wheel principle. Their column wheels control basic functions: start, stop and reset. Depending on the oscillator, events can be measured with an accuracy of one-fifth or one-sixth of a second and, thanks to the minute counter, can last as long as 30 minutes.

Applications of the chronograph function

Chronographs can be used in many different ways. Apart from simply stopping times, they can perform additive time measurements, for instance, by sequencing several laps. For this purpose, the chronograph hands are not reset after stopping, but instead restarted.

The outermost scale of a chronograph covers further applications. Some models feature tachometer scales. They are used to determine an average speed over a distance of one kilometre. If the watch has a pulsometer scale, it can measure a person’s heart rate.

The 1815 CHRONOGRAPH
features a scale for heart rate measurements

The peripheral tachymeter scale of the DATOGRAPH
UP/DOWN

An additional hand for the rattrapante function

“Rattrapante” is a French term that denotes the split-seconds hand of a chronograph. This additional seconds hand can be stopped independently of the chronograph hand and resynchronised with it at will.

Initially, both hands are directly superposed so that only the rattrapante hand is visible. When a measurement is started, both hands begin to run together and the chrono sweep-seconds hand remains concealed. It only becomes visible when measurement of the first event is stopped. At this point, the rattrapante hand stops while the chronograph hand continues to measure the elapsed time. It, too, stands still when measurement of the second event is stopped. This allows for the comparison of two time measurements with the same start time, such as the lap durations of two runners.

A further function is available if the chrono sweep-seconds hand is not stopped: Pressing a button realigns the stopped rattrapante hand with the chrono sweep-seconds hand; both hands will then run together until the rattrapante hand is stopped anew. It is a process that can be repeated any number of times. This makes it possible to measure one aggregate time and several lap times – for instance, the individual lap times of a horse in a race and its total time.

By cleverly combining the functions of the chronograph and rattrapante mechanism, many comparative measurements can be performed relative to a reference time. A rattrapante chronograph can even measure minima and maxima, such as the fastest or slowest of many laps.